This invention relates to discharge lamps such as fluorescent lamps, and more particularly relates to starting aids for such lamps which are expandable to accommodate normal variations in lamp bulb diameter.
It is well known that lamp starting voltage is a function of surface resistance of a fluorescent lamp, and that starting voltage may be reduced by laying a conducting stripe or film on the inner or outer surface of the lamp bulb. See Electric Discharge Lamps, John F. Waymouth, The MIT Press, Cambridge, Mass., 1978, p. 69.
It is also known to improve starting voltage by applying starting aids around the periphery of the bulb in the vicinity of the electrodes. See U.S. Pat. Nos. 4,463,280 and 4,468,591. These starting aids are in the form of conductive bands in contact with the outer glass surface of the bulb.
In one design, this starting band is in the form of a split ring which is secured in place with adhesive tape. The split ring accommodates the normal variation in bulb diameter encountered in mass production. However, the taping operation tends to be labor intensive and does not always result in the firm contact needed for improved starting.
Accordingly, it is an object of this invention to provide an improved starting aid for discharge lamps which will accommodate different bulb diameters without requiring a separate attachment operation.
It is another object of the invention to provide such an improved starting aid which will make the firm contact with the bulb surface needed for improved starting regardless of bulb diameter.